A. Field of Invention
This invention pertains to the art of methods and apparatuses regarding air operated double diaphragm pumps and more specifically to methods and apparatuses regarding the efficient control and operation of air operated pumps, including without limitation, air operated double diaphragm pumps.
B. Description of the Related Art
Fluid-operated pumps, such as diaphragm pumps, are widely used particularly for pumping liquids, solutions, viscous materials, slurries, suspensions or flowable solids. Double diaphragm pumps are well known for their utility in pumping viscous or solids-laden liquids, as well as for pumping plain water or other liquids, and high or low viscosity solutions based on such liquids. Accordingly, such double diaphragm pumps have found extensive use in pumping out sumps, shafts, and pits, and generally in handling a great variety of slurries, sludges, and waste-laden liquids. Fluid driven diaphragm pumps offer certain further advantages in convenience, effectiveness, portability, and safety. Double diaphragm pumps are rugged and compact and, to gain maximum flexibility, are often served by a single intake line and deliver liquid through a short manifold to a single discharge line.
Although known diaphragm pumps work well for their intended purpose, several disadvantages exist. Air operated double diaphragm (AODD) pumps are very inefficient when compared to motor driven pumps. This is due, in large part, to the compressibility of air used to drive the pump and the inefficiency of compressed air systems. AODD pumps normally operate in the 3-5% efficiency range, while centrifugal and other rotary pumps normally operate in the 50-75% efficiency range. Additionally, conventional double diaphragm pumps do not allow the user to retrieve pump performance information for use in controlling the pumping process.
U.S. Pat. No. 5,332,372 to Reynolds teaches a control system for an air operated diaphragm pump. The control system utilizes sensors to monitor pump speed and pump position and then controls the supply of compressed air to the pump in response thereto. Because pump speed and pump position are effected by pumped fluid characteristics, the control unit is able to change the pump speed or the cycle pattern of the pump assembly in response to changes in pumped fluid characteristics to achieve desired pump operating characteristics. The sensors provide a constant feedback that allows the control system to immediately adjust the supply of compressed air to the pump in response to changes in pump operating conditions without interrupting pump operation. Position sensors may be used to detect pump position. For example, the sensors can comprise a digitally encoded piston shaft operatively connected to the diaphragm assembly that provides a precise signal corresponding to pump position that can be used to detect changes in pump speed and pump position. Flow condition sensors can be utilized to determine flow rate, leakage, or slurry concentration. The sensors transmit signals to a microprocessor that utilizes the transmitted signals to selectively actuate the pump's control valves. By sensing changes in pump position, the control system can control the supply of compressed air to the pump by modifying the settings of the control valves thereby controlling both pump speed and pump cycle pattern at any point along the pump stroke. Digital modulating valves can be utilized to increase the degree of system control provided by the control system. The desired optimal pump conditions can be programmed into the control system and, utilizing information transmitted by the sensors, the control system can experiment with different stroke lengths, stroke speeds, and onset of pumping cycle to determine the optimal pump actuation sequence to achieve and maintain the desired predetermined pumping conditions.
U.S. Pat. No. 5,257,914 to Reynolds teaches an electronic control interface for a fluid powered diaphragm pump. Further, the '372 patent is incorporated into the '914 patent by reference. The supply of compressed air is controlled for the purpose of allowing changes in pump speed or a cycle pattern. This is accomplished by detecting the position and acceleration of the diaphragms. More specifically, the pump utilizes sensors to detect certain pump characteristics, such as pump speed, flow rate, and pump position, but not limited thereto, and sends those signals to the control unit. Because the position and rate of movement of the diaphragm is effected by pumped fluid characteristics, the control unit is able to change the pump speed or cycle pattern of the pump assembly in response to changes in pumped fluid characteristics. The control unit determines elapsed time between pulse signals, which leads to calculations for the speed of reciprocation of the rod and the diaphragms. The control unit, utilizing the changes in the speed of travel of the diaphragms, calculates acceleration and other speed-dependent characteristics of the pump.
U.S. Patent Publication No. 2006/0104829 to Reed et al. discloses a control system for operating and controlling an air operated diaphragm pump. Reed does not use position or acceleration of the diaphragms, but is dependent upon other considerations such as a predetermined time period.
What is needed then is an air operated diaphragm pump that utilizes a self learning process by velocity detection at a floating point or a set point to minimize the amount of compressed air needed to effectively operate the pump.